Timing mechanism

ABSTRACT

A timing mechanism for household appliances is shown to comprise a ratchet, sequence control means movable with the ratchet for regulating performance of appliance functions, and a pawl reciprocally movable for advancing the ratchet. A spring biases the pawl in one direction and an actuator element intermittently moves the pawl in the opposite direction against the spring bias. The actuator element is formed of a nickel-titanium alloy and is deformed from an original configuration to a second configuration as the pawl is moved in response to the spring bias. The actuator is adapted to abruptly return to its original configuration for moving the pawl in the opposite direction against the spring bias to advance the ratchet when the actuator alloy is heated above the transition temperature. Switch means are opened and closed as the pawl is moved, for electrically heating the actuator to its transition temperature and for alternately permitting the actuator to cool below its transition temperature.

Flanagan i111 3,822,413 l 5l July 2,1974

I5 1 TIMING MECHANISM,

[75] Inventor: Charles D. Flanagan, Attleboro,

Mass. Y i

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: Apr. 30, 1973' [21] Appl. No.: 355,850

52] US. Cl. 337/127, 337/139 [51] Int. Cl. H0lh6'1/02, H0111 61/06 [58] Field of Search 337/123, 126, 127, 138,

Primary Examiner-Roy N. Envall, Jr. Attorney, Agent, or Firml-larold Levine; John A. Haug; James P. McAndrews [57] 7 ABSTRACT A timing mechanism for household appliances is shown to comprise a ratchet, sequence control means movable with the ratchet for regulating performance of appliance functions, and a pawl reciprocally movable for advancing the ratchet. A spring biases the pawl in one direction and an actuator element intermittently moves the pawl in the opposite direction against the spring bias. The actuator element is formed of a nickel-titanium alloy and is deformed from an originalconfiguration to a second configuration as the pawl is moved in response to the spring bias. Theactuator is adapted to abruptly return to its original configuration for moving the pawl in the opposite direction against the spring bias to advance the ratchet when theactuator alloy is heated above the transition temperature. Switch means are opened and closed as the pawl is moved, for electrically heating the actuator to its transition temperature and foralternately permitting the actuator to cool below its transition temperature.

6 Claims, 1 Drawing Figure 1 TIMING MECHANISM Many conventional household appliances incorporate complex and expensive timing mechanisms for regulating the performance cycles of the appliances. Typically, for example, the timing mechanisms include synchronous motors, sequence control drums or the like, and escapement mechanisms for coupling the motors to the drums. lt'would be desirable to provide improved timing mechanisms, preferably utilizing improved stepping motors or the like, which are significantly less complex and expensive while still achieving high device reliability. Most important, the conventional timing mechanisms are frequently operable only at relatively high power levels. With the recent development of low power integrated circuit control systems for such appliances, it wouldalso be desirable to provide improved timing mechanisms which are operable at significantly lower power levels.

It is an object of this-invention to provide a novel and improved stepping motor; to provide a novel and im.- proved timing mechanism utilizing such a stepping mtor; to provide such an improved timing mechanism which is adapted to regulate the performance cycles of various household appliances; 1 to provide such improved mechanisms which are of simple and inexpensive construction; to provide such improved mechanisms which are compact, rugged and reliable; and to provide such mechanisms which are operable at very low power levels.

Other objects and advantages of the improved stepping motor and timing mechanism of this invention appear in the following detailed description of preferred embodiments of the invention, the detailed description referring to the drawing which comprises a perspective view of the timing mechanism of this invention utilizing the improved stepping motor of this invention.

Referring to the drawing, the novel and improved timing mechanism of this invention is indicated at and is shown to include a base or frame 12 of suitably strong and rigid, electrically insulating material such as a phenolic resin which mounts the shaft 14 or other motor output means forfree rotation on the frame. The timing mechanism also includes a sequence control means 16 of any conventional type represented in the drawing by the cams 18 and 20 and by the switches 22 and 24. As will be understood, each of the noted switches includes a pair of spring contact arms 26 and 28 which carry respective contacts 30 and 32 and which are cantilever mounted on the frame 12 in electrically insulated relation to each other for normally holding the contacts 30 and 32 disengaged in an open circuit position. However, the resilient contact arms 26 are adapted to be moved upward for engaging the contacts 30 with the stationary or otherwise complementary contacts 32 to close the output circuits of the timing mechanism. As will be understood, closing of these output circuits is effective to energize various devices outside the mechanism 10 as represented in the drawing by the terminals 34 and 36. The earns 18 and 20 each have high or camming portions 18.1 and 20.1 of selected lengths and have low or dwell portions 18.2

and 20.2, also of elected lengths. The cams aremounted on the shaft 14 for rotation with the shaft and are proportional so that, as the cams are rotated with the shaft as indicated by the arrow 37, the high portions of the cams selectively engage and raise the resilient the timing mechanism for selected periods of time. A]-

temately, of course, as the dwell portions of the cams are moved past the contact arms 26, the arms 26 are permitted to resiliently withdraw thecontacts 30 from engagement with the contacts 32 and to open the output circuits of the mechanism for selected periods of time. Any desired number of cams can be mounted on the shaft for cooperating with respective output switches within the scope of this invention. Alternately,

the illustrated sequence control means 16 of the mechanism, shown as being formed of cams and spring switches, could be also formed of a timing drum which is rotatable with the shaft and which is .cooperable with appropriate sliding contacts within the scope of this invention. Other conventional sequence control means could also be used.

In accordance with this invention, an improved stepping motor indicated at 37 is shown to include a ratchet wheel 38 which is also mounted on the motor output shaft 14 for rotation with the shaft. In addition, an actuator element 40 is connected, preferably in series with a selected resistive element 42-, and preferably with a length of wire 43, between a control terminal 44 and a spring member 46 both of which are preferably cantilever mounted as shown in the drawing. The spring m em ber 46 carries a contact 48 and is normally biased by its inherent resilience to engage the contact 48 with a complementary contact 50 carried by a second control terminal 52 which is also cantilever mounted on the frame 12, thereby to close a control circuit of the mechanism. As will be understood, electrical current is adapted to be directed through this control circuit from a source'outside the mechanism as represented in the drawing by terminals 54 and 56 A pawl 58 is carried on the actuator element 40 and is arranged so that reciprocal movement of the pawl in the direction indicated by the arrow 59 is adapted to engage the ratchet wheel 38 as the pawl is moved in one direction, downwardly as shown in the drawing, for advancing or rotating the ratchet in the direction of the arrow 37 and to alternately slide past the ratchet as the pawl moves in the opposite direction.

In accordance with this invention, the actuator element 40 comprises a length of wire of a selected nickeltitanium alloy having a composition by weight of from about 54 to 56 percent nickel and the balance titanium. As this metal alloy is well known, the alloy is not further described herein and it will be understood that'this alloy displays a relatively low modulus of elasticity at a temperature below a predetermined transitiontem perature which is characteristic of the alloy, the alloy then displaying a relatively much higher modulus of elasticity at a temperature above this'transition temperature. When properly conditioned in well known manner, the material is also adapted to display remarkable shape memory properties as the material is heated through its transition temperaturerange. For example, when the alloy material of the wire 40 is deformed while below its transition temperature by drawing the wire to increase the wire length up to about 8 percent, the wire is adapted to subsequently display remarkable shape memory and to sharply shorten in length when the wire is thereafter heated above its transition temperature. After subsequent cooling of the wire below its transition temperature, the wire is again easily deformed by drawing or stretching to again prepare the wire for displaying its shapememory. Typically, for example, the wire 40 is formed of a nickel-titanium alloy comprising about 55 percent nickel, by weight, and the balance titanium, this alloy having a transition temperature at about 60 C. and having other physical properties as follows:

Utimate tensile strength 125,000 psi Density 6.5 g./cc.

Heat capacity 0.077 cal/degreeC/g. Resistivity 80 X IO ohm-centimeters Youngs Modulus (below transition temperature) 3 X 10" psi Youngs Modulus (above transition temperature) l2 X l psi length by about 4 percent, and to normally engage the contact 48 with the contact 50 for closing the control circuit of the timing mechanism while maintaining the actuator under stress. Accordingly, electrical current is adapted to be directed through the control circuit through the actuator wire 40 for electrically selfheating the wire 40 above its transition temperature so that the wire 40 is sharply shortened in length and sharply increased in modulus of elasticity for moving the pawl 58 to advance the ratchet wheel 38 and for moving the spring member 46 against its bias to open the control circuit of the timing mechanism. When the control circuit of the mechanism is thus opened, the actuator wire 40 is permitted to cool below its transition temperature and, as the wire again displays its relatively low modulus of elasticity, the spring 46 again stretches the wire for moving the pawl 58 back past the ratchet wheel into a position for again advancing the ratchet when the wire 40 is next heated. In this way the application of an electrical current through the control circuit of the timing mechanism for a selected period of time operates the stepping motor 37 for that period and is adapted to advance the ratchet when the wire 40 is next heated. In this way the application of an electrical current through the control circuit of the timing mechanism for a selected period of time operates the stepping motor 37 for that period and is adapted to advance the ratchet 38 to a selected extent within that period of time and to rotate the cams l8 and 20 of the sequence control means 16 for regulating opening and closing of the output circuits of the mechanism. It should be understood that although a particular structure has been shown for use in intermittently heating the actuator element 40 above its transition temperature other conventional intermittent heating means could also be used within the scope of this invention.

Where both a heating and a cooling of the actuator wire 40 is utilized in moving the pawl 58 through one cycle for advancing the ratchet 38 one notch as abovedescribed, the effect of an increase in ambient temperature in causing more rapid heating of the wire is effectively cancelled out during cooling of the wire by the effect of the higher ambient temperature in retarding cooling of the wire. Thus, the rate of operation of the device is not altered by changes in ambient tempera- 4 ture. That is,,the composite heating and cooling time for the actuator wire is essentially constant at various ambient temperatures. Where the actuator wire also displays such high modulus of elasticity during the pawl movement which effects advancement of the ratchet 38, a relatively fine diameter actuator wire 40 is effective to rotate the sequence control means 16 while being adapted to be heated witha relatively low input of electrical energy. Typically, for example, the actuator wire 40 can have a diameter of 0.002 inches or less and is adapted to be heated from room temperature to its transition temperature with about 2 watts or less of electrical energy at the low power levels compatible with the power levels used in energizing integrated circuit control systems.

It should be understood that, although a preferred embodiment of the stepping motor and timing mechanism of this invention have been described by way of illustrating the invention, various modifications and equivalents of the disclosed embodiment could be utilized for achieving the advantages of this invention. For example, the control terminals 44 and 52 can be formed of deformable materials for-permitting adjustment of the stress applied to the actuator 40 by the spring 46 and for adjusting contact pressure between the control contacts 48 and 50. Further, although the ratchet 38 is shown as a wheel arranged to rotate earns 18 and 20, the ratchet could be linear in form and could be arranged to move various conventional sequence control'means within the scope of this invention. Further, various conventional means can be incorporated in the mechanism 10 to provide selected mechanical advantage in transmitting the noted movement of the actuator element to the noted sequence control means of the mechanism. This invention includes all modifications and equivalents of the disclosed embodiment of the invention that fall within the scope of the appended claims.

I claim:

1. A timing mechanism comprising ratchet means, sequence control means movable with said ratchet means, pawl means reciprocally movable for advancing said ratchet means, spring means biasing the pawl means for movement in one direction into a position for subsequently advancing said ratchet means actuator means of a selected metal alloy arranged to be deformed from an original configuration to a second configuration as said pawl means is moved in said one direction in response to said spring bias while said alloy displays a relatively low modulus of elasticity below a transition temperature and to abruptly return to its original configuration and to display a relatively higher modulus of elasticity for moving said pawl means in an opposite direction against said bias so that said pawl movement in said opposite direction moves said ratchet means to a selected extent when said alloy is heated above said transition temperature, and means for intermittently heating said actuator means above said transition temperature so that pawl movement in said opposite direction moves said ratchet means to a selected extent each time said actuator means is heated above said transition temperature.

2. A timing mechanism as set forth in claim 1 wherein said actuator means embodies a wire of a nickeltitanium alloy having a composition, by weight, of from about 54 to 56 percent nickel and the balance titanium. said wire being of a diameter of about 0.002 inches or less which is heatable from room temperature to said transition temperature with an energy input of less than about 2 watts. I

3. A timing mechanism comprising ratchet means, sequence control means movable with said ratchet means, pawl means movable for advancing said ratchet means, spring means biasing the pawl means for movement in one direction, actuator means of a selected metal alloy arranged to be deformed from an original configuration toa second configuration as said pawl means is moved in response to said spring bias while said alloy displays a relatively low modulus of elasticity below a transition temperature and to abruptly return to its original configuration and to display a relatively higher modulus of elasticity for moving said pawl means in an opposite direction against said bias for advancing said ratchet means when said alloy is heated above said'transition temperature, and means for intermittently heating said actuator means above said transition temperature, said means for intermittently heating said actuator means comprising contact means movable with saidpawl means to open and close an electrical circuit for directing electrical current intermittently 1 through said actuator means for electrically selfheating said actuator means to said transition temperature. r

4. A timing 'mechanismas set forth in claim 1 wherein said ratchet means comprises a ratchet wheel mounted for rotation as said ratchet wheel is advanced by said pawl means, and wherein said sequence control means comprise normally open spring switch means and cam means rotatablewith said ratchet wheel for selectively closing said switch means.

5. A timing mechanism comprising a frame of electrically insulating material, a shaft rotatablyvmounted on said base, a ratchet wheel mounted on said shaft for rotation with said shaft, a first output contact mounted on said frame, an output spring arm cantilever mounted on said frame and carrying a movable output contact for engagement with said first output contact to close an output circuit, cam means mounted on said shaft for rotation with said ratchet wheel to selectively engage said output spring arm for moving said arm to selectively engage said movable output contact with said first output contact, a first control contact mounted on said frame, a control spring member cantilever mounted on said frame and carrying a mmovable control contact normallybiased by said control spring arm into engagement with said first control contact to close 6 a' control circuit, a control terminal mounted on said frame, a metal actuator wire of a nickel-titanium metal alloy electrically connected between said control spring member and'said control terminal, said metal wire being adapted to be deformed from an original length to a second length as said control spring member moves said movable control contact to engage said first control contact while said metal alloy displays a relative low modulus of elasticity below a transition temperature for permitting electrical current to flow in said control circuit to electrically heat said wire to said transition temperature, said metal wire being adapted to abruptly return to its original length and to display a relatively higher modulus, of elasticity when heated above its transition temperature to move said control spring arm against its bias to open said control circuit for permitting said wire to cool below said transition temperature and to be again deformed to said second length by said spring bias, and a pawl carried by said ac tuator wire for engagement with said ratchet wheel to rotate said wheel when said actuator wire abruptly returns to its original length, whereby directing electrical current through said control circuit is adapted to regulate opening and closing of said output circuit.

6. A stepping motor comprising ratchet means, pawl means reciprocally movable for advancing said ratchet means, spring means biasing said pawl means for movement in one direction into a position for subsequently advancing said ratchet means, actuator means of a selected metal alloy arranged to be-de formed from an original configuration to a second configuration as said pawl means is moved in said one direction in response to said spring bias while said alloy displays a relatively low modulus of elasticity below a transition temperature and to abruptly return toits original configuration and to display a relatively higher modulus of elasticity for moving said pawl means in an opposite direction against said bias so that said pawl movement in said opposite direction moves said ratchet means to a selected extent when said alloy is heated above said transition temperature, means for intermittently heating said actuator means above said transition temperature so that pawl movement in-said opposite direction moves said ratchet means to a selected extent each time said actuator means is heated above said transition temperature, and motor output means movable with said ratchet means.

ak i 

1. A timing mechanism comprising ratchet means, sequence control means movable with said ratchet means, pawl means reciprocally movable for advancing said ratchet means, spring means biasing the pawl means for movement in one direction into a position for subsequently advancing said ratchet means actuator means of a selected metal alloy arranged to be deformed from an original configuration to a second configuration as said pawl means is moved in said one direction in response to said spring bias while said alloy displays a relatively low modulus of elasticity below a transition temperature and to abruptly return to its original configuration and to display a relatively higher modulus of elasticity for moving said pawl means in an opposite direction against said bias so that said pawl movement in said opposite direction moves said ratchet means to a selected extent when said alloy is heated above said transition temperature, and means for intermittently heating said actuator means above said transition temperature so that pawl movement in said opposite direction moves said ratchet means to a selected extent each time said actuator means is heated above said transition temperature.
 2. A timing mechanism as set forth in claim 1 wherein said actuator means embodies a wire of a nickel-titanium alloy having a composition, by weight, of from about 54 to 56 percent nickel and the balance titanium, said wire being of a diameter of about 0.002 inches or less which is heatable from room temperature to said transition temperature with an energy input of less than about 2 watts.
 3. A timing mechanism comprising ratchet means, sequence control means movable with said ratchet means, pawl means movable for advancing said ratchet means, spring means biasing the pawl means for movement in one direction, actuator means of a selected metal alloy arranged to be deformed from an original configuration to a second configurAtion as said pawl means is moved in response to said spring bias while said alloy displays a relatively low modulus of elasticity below a transition temperature and to abruptly return to its original configuration and to display a relatively higher modulus of elasticity for moving said pawl means in an opposite direction against said bias for advancing said ratchet means when said alloy is heated above said transition temperature, and means for intermittently heating said actuator means above said transition temperature, said means for intermittently heating said actuator means comprising contact means movable with said pawl means to open and close an electrical circuit for directing electrical current intermittently through said actuator means for electrically self-heating said actuator means to said transition temperature.
 4. A timing mechanism as set forth in claim 1 wherein said ratchet means comprises a ratchet wheel mounted for rotation as said ratchet wheel is advanced by said pawl means, and wherein said sequence control means comprise normally open spring switch means and cam means rotatable with said ratchet wheel for selectively closing said switch means.
 5. A timing mechanism comprising a frame of electrically insulating material, a shaft rotatably mounted on said base, a ratchet wheel mounted on said shaft for rotation with said shaft, a first output contact mounted on said frame, an output spring arm cantilever mounted on said frame and carrying a movable output contact for engagement with said first output contact to close an output circuit, cam means mounted on said shaft for rotation with said ratchet wheel to selectively engage said output spring arm for moving said arm to selectively engage said movable output contact with said first output contact, a first control contact mounted on said frame, a control spring member cantilever mounted on said frame and carrying a mmovable control contact normally biased by said control spring arm into engagement with said first control contact to close a control circuit, a control terminal mounted on said frame, a metal actuator wire of a nickel-titanium metal alloy electrically connected between said control spring member and said control terminal, said metal wire being adapted to be deformed from an original length to a second length as said control spring member moves said movable control contact to engage said first control contact while said metal alloy displays a relative low modulus of elasticity below a transition temperature for permitting electrical current to flow in said control circuit to electrically heat said wire to said transition temperature, said metal wire being adapted to abruptly return to its original length and to display a relatively higher modulus of elasticity when heated above its transition temperature to move said control spring arm against its bias to open said control circuit for permitting said wire to cool below said transition temperature and to be again deformed to said second length by said spring bias, and a pawl carried by said actuator wire for engagement with said ratchet wheel to rotate said wheel when said actuator wire abruptly returns to its original length, whereby directing electrical current through said control circuit is adapted to regulate opening and closing of said output circuit.
 6. A stepping motor comprising ratchet means, pawl means reciprocally movable for advancing said ratchet means, spring means biasing said pawl means for movement in one direction into a position for subsequently advancing said ratchet means, actuator means of a selected metal alloy arranged to be deformed from an original configuration to a second configuration as said pawl means is moved in said one direction in response to said spring bias while said alloy displays a relatively low modulus of elasticity below a transition temperature and to abruptly return to its original configuration and to display a relatively higher modulus of elasticity for moving said pawl means in an opposIte direction against said bias so that said pawl movement in said opposite direction moves said ratchet means to a selected extent when said alloy is heated above said transition temperature, means for intermittently heating said actuator means above said transition temperature so that pawl movement in said opposite direction moves said ratchet means to a selected extent each time said actuator means is heated above said transition temperature, and motor output means movable with said ratchet means. 